A randomly chosen star in today's universe is most likely to live in a galaxy with stellar mass between the Milky Way and Andromeda. It remains uncertain, however, how the structural evolution of ...these bulge-disk systems proceeded. Most of the unobscured star formation we observe by building Andromeda progenitor s at 0.7 < z < 1.5 occurs in disks, but 90% of their star formation is reprocessed by dust and remains unaccounted for. Here we map rest-500 m dust continuum emission in an Andromeda progenitor at z = 1.25 to probe where it is growing through dust-obscured star formation. Combining resolved dust measurements from the NOthern Extended Millimeter Array interferometer with Hubble Space Telescope H maps and multicolor imaging (including new data from the Hubble Deep UV Legacy Survey, HDUV), we find a bulge growing by dust-obscured star formation: while the unobscured star formation is centrally suppressed, the dust continuum is centrally concentrated, filling the ring-like structure that is evident in the H and UV emission. Reflecting this, the dust emission is more compact than the optical/UV tracers of star formation with re(dust) = 3.4 kpc, re(H )/re(dust) = 1.4, and re(UV)/re(dust) = 1.8. Crucially, however, the bulge and disk of this galaxy are building simultaneously; although the dust emission is more compact than the rest-optical emission (re(optical)/re(dust) = 1.4), it is somewhat less compact than the stellar mass (re(M*)/re(dust) = 0.9). Taking the rest-500 m emission as a tracer, the expected structural evolution can be accounted for by star formation: it will grow in size by Δre/ΔM* ∼ 0.3 and in central surface density by Δ cen/ΔM* ∼ 0.9. Finally, our observations are consistent with a picture in which merging and disk instabilities drive gas to the center of galaxies, boosting global star formation rates above the main sequence and building bulges.
Abstract
We present a cross-calibration of CO- and dust-based molecular gas masses at z ≤ 0.2. Our results are based on a survey with the IRAM 30-m telescope collecting CO(1–0) measurements of 78 ...massive (logM⋆/M⊙> 10) galaxies with known gas-phase metallicities and with IR photometric coverage from Wide-field Infrared Survey Explorer(WISE; 22 $\mu$m) and Herschel Spectral and Photometric Imaging Receiver (SPIRE; 250, 350, 500$\mu$m). We find a tight relation (∼0.17 dex scatter) between the gas masses inferred from CO and dust continuum emission, with a minor systematic offset of 0.05 dex. The two methods can be brought into agreement by applying a metallicity-dependent adjustment factor (∼0.13 dex scatter). We illustrate that the observed offset is consistent with a scenario in which dust traces not only molecular gas but also part of the Hi reservoir, residing in the H2-dominated region of the galaxy. Observations of the CO(2–1) to CO(1–0) line ratio for two-thirds of the sample indicate a narrow range in excitation properties, with a median ratio of luminosities ⟨R21⟩ ∼ 0.64. Finally, we find dynamical mass constraints from spectral line profile fitting to agree well with the anticipated mass budget enclosed within an effective radius, once all mass components (stars, gas, and dark matter) are accounted for.
We present spatially resolved ALMA observations of the CO emission line in two massive galaxies at z = 2.5 on the star-forming main sequence. Both galaxies have compact dusty star-forming cores with ...effective radii of and in the 870 m continuum emission. The spatial extent of star-forming molecular gas is also compact with and , but more extended than the dust emission. Interpreting the observed position-velocity diagrams with dynamical models, we find the starburst cores to be rotation dominated with the ratio of the maximum rotation velocity to the local velocity dispersion of ( km s−1) and ( km s−1). Given that the descendants of these massive galaxies in the local universe are likely ellipticals with nearly an order of magnitude lower, the rapidly rotating galaxies would lose significant net angular momentum in the intervening time. The comparisons among dynamical, stellar, gas, and dust mass suggest that the starburst CO-to-H2 conversion factor of (K km s−1 pc−2)−1 is appropriate in the spatially resolved cores. The dense cores are likely to be formed in extreme environments similar to the central regions of local ultraluminous infrared galaxies. Our work also demonstrates that a combination of medium-resolution CO and high-resolution dust continuum observations is a powerful tool for characterizing the dynamical state of molecular gas in distant galaxies.
ABSTRACT
We exploit deep integral-field spectroscopic observations with KMOS/Very Large Telescope of 240 star-forming disks at
to dynamically constrain their mass budget. Our sample consists of ...massive (
) galaxies with sizes
. By contrasting the observed velocity and dispersion profiles with dynamical models, we find that on average the stellar content contributes
of the total dynamical mass, with a significant spread among galaxies (68th percentile range
). Including molecular gas as inferred from CO- and dust-based scaling relations, the estimated baryonic mass adds up to
of the total for the typical galaxy in our sample, reaching
at
. We conclude that baryons make up most of the mass within the disk regions of high-redshift star-forming disk galaxies, with typical disks at
being strongly baryon-dominated within
R
e
. Substantial object-to-object variations in both stellar and baryonic mass fractions are observed among the galaxies in our sample, larger than what can be accounted for by the formal uncertainties in their respective measurements. In both cases, the mass fractions correlate most strongly with measures of surface density. High-
galaxies feature stellar mass fractions closer to unity, and systems with high inferred gas or baryonic surface densities leave less room for additional mass components other than stars and molecular gas. Our findings can be interpreted as more extended disks probing further (and more compact disks probing less far) into the dark matter halos that host them.
Abstract
Quasar feedback may regulate the growth of supermassive black holes, quench coeval star formation, and impact galaxy morphology and the circumgalactic medium. However, direct evidence for ...quasar feedback in action at the epoch of peak black hole accretion at
z
≈ 2 remains elusive. A good case in point is the
z
= 1.6 quasar WISEA J100211.29+013706.7 (XID 2028), where past analyses of the same ground-based data have come to different conclusions. Here, we revisit this object with the integral-field unit of the Near Infrared Spectrograph on board the JWST as part of Early Release Science program Q3D. The excellent angular resolution and sensitivity of the JWST data reveal new morphological and kinematic substructures in the outflowing gas plume. An analysis of the emission-line ratios indicates that photoionization by the central quasar dominates the ionization state of the gas with no obvious sign for a major contribution from hot young stars anywhere in the host galaxy. The rest-frame near-UV emission aligned along the wide-angle cone of outflowing gas is interpreted as a scattering cone. The outflow has cleared a channel in the dusty host galaxy, through which some of the quasar ionizing radiation is able to escape and heat the surrounding interstellar and circumgalactic media. Although the warm ionized outflow is not powerful enough to impact the host galaxy via mechanical feedback, radiative feedback by the active galactic nucleus, aided by the outflow, may help to explain the unusually small molecular gas mass fraction in the galaxy host.
ABSTRACT
We contrast the gas kinematics and dark matter contents of z = 2 star-forming galaxies (SFGs) from state-of-the-art cosmological simulations within the ΛCDM framework to observations. To ...this end, we create realistic mock observations of massive SFGs ($M_*\gt 4\times 10^{10} \, \mathrm{M}_{\odot}$, SFR >50 M⊙ yr−1) from the TNG50 simulation of the IllustrisTNG suite, resembling near-infrared, adaptive-optics assisted integral-field observations from the ground. Using observational line fitting and modelling techniques, we analyse in detail the kinematics of seven TNG50 galaxies from five different projections per galaxy, and compare them to observations of twelve massive SFGs by Genzel et al. (2020). The simulated galaxies show clear signs of disc rotation but mostly exhibit more asymmetric rotation curves, partly due to large intrinsic radial and vertical velocity components. At identical inclination angle, their 1D velocity profiles can vary along different lines of sight by up to Δv = 200 km s−1. From dynamical modelling we infer rotation speeds and velocity dispersions that are broadly consistent with observational results. We find low central dark matter fractions compatible with observations ($f_{\rm DM}^v(\lt R_e)=v_{\rm DM}^2(R_e)/v_{\rm circ}^2(R_e)\sim 0.32\pm 0.10$), however for disc effective radii Re that are mostly too small: at fixed Re the TNG50 dark matter fractions are too high by a factor of ∼2. We speculate that the differences in gas kinematics and dark matter content compared to the observations may be due to physical processes that are not resolved in sufficient detail with the numerical resolution available in current cosmological simulations.
Abstract
We present a detailed study of the molecular gas content and stellar population properties of three massive galaxies at 1 <
z
< 1.3 that are in different stages of quenching. The galaxies ...were selected to have quiescent optical/near-infrared spectral energy distribution and relatively bright emission at 24
μ
m, and show remarkably diverse properties. CO emission from each of the three galaxies is detected in deep NOEMA observations, allowing us to derive molecular gas fractions
M
gas
/
M
*
of 13%–23%. We also reconstruct the star formation histories by fitting models to the observed photometry and optical spectroscopy, finding evidence for recent rejuvenation in one object, slow quenching in another, and rapid quenching in the third system. To better constrain the quenching mechanism we explore the depletion times for our sample and other similar samples at
z
∼ 0.7 from the literature. We find that the depletion times are highly dependent on the method adopted to measure the star formation rate: using the UV+IR luminosity we obtain depletion times about 6 times shorter than those derived using dust-corrected O
ii
emission. When adopting the star formation rates from spectral fitting, which are arguably more robust, we find that recently quenched galaxies and star-forming galaxies have similar depletion times, while older quiescent systems have longer depletion times. These results offer new, important constraints for physical models of galaxy quenching.
Abstract
Massive galaxies formed most actively at redshifts
z
= 1–3 during the period known as “cosmic noon.” Here we present an emission-line study of the extremely red quasar ...SDSSJ165202.64+172852.3’s host galaxy at
z
= 2.94, based on observations with the Near Infrared Spectrograph integral field unit on board JWST. We use standard emission-line diagnostic ratios to map the sources of gas ionization across the host and a swarm of companion galaxies. The quasar dominates the photoionization, but we also discover shock-excited regions orthogonal to the ionization cone and the quasar-driven outflow. These shocks could be merger-induced or—more likely, given the presence of a powerful galactic-scale quasar outflow—these are signatures of wide-angle outflows that can reach parts of the galaxy that are not directly illuminated by the quasar. Finally, the kinematically narrow emission associated with the host galaxy presents as a collection of 1 kpc–scale clumps forming stars at a rate of at least 200
M
⊙
yr
−1
. The interstellar medium within these clumps shows high electron densities, reaching up to 3000 cm
−3
, with metallicities ranging from half to a third solar with a positive metallicity gradient, and
V
-band extinctions up to 3 mag. The star formation conditions are far more extreme in these regions than in local star-forming galaxies but consistent with those of massive galaxies at cosmic noon. The JWST observations simultaneously reveal an archetypal rapidly forming massive galaxy undergoing a merger, a clumpy starburst, an episode of obscured near-Eddington quasar activity, and an extremely powerful quasar outflow.
We present ∼1″ resolution (∼2 kpc in the source plane) observations of the CO (1–0), CO (3–2), Hα, and N ii lines in the strongly lensed z = 2.26 star-forming galaxy SDSS J0901+1814. We use these ...observations to constrain the lensing potential of a foreground group of galaxies, and our source-plane reconstructions indicate that SDSS J0901+1814 is a nearly face-on (i ≈ 30°) massive disk with r 1/2 ≳ 4 kpc for its molecular gas. Using our new magnification factors (μ tot ≈ 30), we find that SDSS J0901+1814 has a star formation rate (SFR) of \({268}_{-61}^{+63}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}\), \({M}_{\mathrm{gas}}=({1.6}_{-0.2}^{+0.3})\times {10}^{11}({\alpha }_{\mathrm{CO}}/4.6)\,{M}_{\odot }\), and \({M}_{\star }=({9.5}_{-2.8}^{+3.8})\times {10}^{10}\,{M}_{\odot }\), which places it on the star-forming galaxy “main sequence.” We use our matched high angular resolution gas and SFR tracers (CO and Hα, respectively) to perform a spatially resolved (pixel-by-pixel) analysis of SDSS J0901+1814 in terms of the Schmidt–Kennicutt relation. After correcting for the large fraction of obscured star formation (\({\mathrm{SFR}}_{{\rm{H}}\alpha }/{\mathrm{SFR}}_{\mathrm{TIR}}={0.054}_{-0.014}^{+0.015}\)), we find that SDSS J0901+1814 is offset from “normal” star-forming galaxies to higher star formation efficiencies independent of assumptions for the CO-to-H2 conversion factor. Our mean best-fit index for the Schmidt–Kennicutt relation for SDSS J0901+1814, evaluated with different CO lines and smoothing levels, is \(\bar{n}=1.54\pm 0.13;\) however, the index may be affected by gravitational lensing, and we find \(\bar{n}=1.24\pm 0.02\) when analyzing the source-plane reconstructions. While the Schmidt–Kennicutt index largely appears unaffected by which of the two CO transitions we use to trace the molecular gas, the source-plane reconstructions and dynamical modeling suggest that the CO (1–0) emission is more spatially extended than the CO (3–2) emission.
Abstract
Quasar-driven galactic outflows are a major driver of the evolution of massive galaxies. We report observations of a powerful galactic-scale outflow in a
z
= 3 extremely red and ...intrinsically luminous (
L
bol
≃ 5 × 10
47
erg s
−1
) quasar SDSSJ1652 + 1728 with the Near-infrared Spectrograph on board JWST. We analyze the kinematics of rest-frame optical emission lines and identify the quasar-driven outflow extending out to ∼10 kpc from the quasar with a velocity offset of (
v
r
= ± 500 km s
−1
) and high velocity dispersion (FWHM = 700–2400 km s
−1
). Due to JWST’s unprecedented surface brightness sensitivity in the near-infrared, we unambiguously show that the powerful high velocity outflow in an extremely red quasar encompasses a large swath of the host galaxy’s interstellar medium. Using the kinematics and dynamics of optical emission lines, we estimate the mass outflow rate—in the warm ionized phase alone—to be at least 2300 ± 1400
M
⊙
yr
−1
. We measure a momentum flux ratio between the outflow and the quasar accretion disk of ∼1 on a kpc scale, indicating that the outflow was likely driven in a relatively high (>10
23
cm
−2
) column density environment through radiation pressure on dust grains. We find a coupling efficiency between the bolometric luminosity of the quasar and the outflow of 0.1%, matching the theoretical prediction of the minimum coupling efficiency necessary for negative quasar feedback. The outflow has sufficient energetics to drive the observed turbulence seen in shocked regions of the quasar host galaxy, which are likely directly responsible for prolonging the time that it takes for gas to cool efficiently.
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